1. Technical Field
The present invention relates to the field of transmission of data over networks. More particularly, the invention provides methods and systems that guarantee throughput of critical data by prioritizing end-to-end data delivery.
2. Related Information
FIG. 1 shows a typical configuration used to exchange data among three locations 100, 102 and 104. The transmission of data from locations 100 and 102 to location 104 will be described to reveal some of the problems associated with prior art networks. A first location 100 contains applications 106 and 108 that provide data to an Ethernet 110. Data is transmitted from Ethernet 110 to a first router 112. Likewise, applications 114 and 116 provide data to a second Ethernet 118 at location 102. Data is transmitted from Ethernet 118 to a second router 120. Routers 112 and 120 transmit data to a frame relay network 122.
Frame relay network 122 contains frame relay switches 124, 126 and 128. Routers 112 and 120 transmit data to frame relay switch 128 via frame relay switches 124 and 126 respectively, Finally, data is transmitted from frame relay switch 128 through a third router 130 and an Ethernet 132 to applications 134 and 136.
Conventional networks, such as the one shown in FIG. 1 have limited bandwidths and, therefore, limited data throughputs. Components such as routers and frame relay switches typically have lower bandwidths than the transmission lines used to connect the components. As a result, the overall throughput and quality of service of a network may be limited by the bandwidth of some of the components, especially the access links of routing and switching components. For example, congestion can occur at output port 138 of router 112 when Ethernet 110 transmits a relatively large number of packets containing data to router 112. Router 112 must encapsulate each of the data packets into a frame relay frame and transmit the frame relay frames to frame relay switch 124. When there is heavy traffic through router 112, the throughput of all of the packets are delayed equally, regardless of the importance of the data contained in the packets. A similar situation may occur at site 102.
Besides congestion possibly occurring at output port 138, congestion can occur further down the path toward a packet's destination, for example at egress link 140. Frame relay frames transmitted from frame relay switches 124 and 126 arrive at frame relay switch 128. Frame relay switches, such as frame relay switch 128, typically have egress access links that have a lower bandwidth than the sum of the bandwidths of the ingress access links. As a result, congestion can occur at egress link 140 of frame relay switch 128 when a relatively large number of frames arrive from frame relay switches 124 and 126. Furthermore, the throughput of each of the frames arriving at frame relay switch 128 is degraded equally, regardless of the importance of the data contained in the packet. Similar problems may result when sending data to sites 100 and 102.
Therefore, there exists a need in the art for a network that allows critical data to receive preference over non-critical data at points of congestion throughout the network to provide a guaranteed throughput for the critical data.